Multistage process of regenerating a fluidized catalyst



July I2, 1949.1' w. l. THOMPSON -l-:r AL l 2,4759650 .'IU'LTISTAGE iROCESS 0F REGENERMING A FLUIDIZBD CATALYS'I Filed Oct. 28, 1943 Patented July l2, 1.949 l v I, l t

MUL'ns'rscE rnocnss or nEGENEna'rlNG w A FLUmrzEp cArALYsr f William I. Thompson, Elisabeth, and Charles W. Tyson, Summit, N. J., assignors to Standard Oil Development Company,v a corporation of Delaware Application October 28, 1943, Serial No. 508,044

s claims. (ci. 25a-411) 'I'his application relates to a method of regenerating Vcatalysts and pertains more particularly to a method of removing combustible deposits from finely-divided catalyst powder.

In such case the cracked products segregated from the powdered material in the cyclone separator are removed `therefrom through line I2 and passed to suitable fractionatlng or purifying equipment for segregation of the desired product It has previously been proposed to crack cata- 5 therefrom. lytically hydrocarbon oils in which the catalyst The spent catalyst separated from the cracked f employed is present in powdered form. In such products passes through a vertical conduit il procedure, the powder is usually dispersed into provided with control valve II-A into a disper- `the stream of oil vapors `to be cracked and the sion chamber it in whichit is intermixed with a resulting dispersion passed through a cracking regenerating gas introduced through line l5. zone. During the course ci" the reaction the Such gas may be air or air diluted with other catalyst becomes contaminated with carbonagas and may be introduced into the system ceous deposits which reduces the activity of the through line it and compressor Il from which it catalyst for bringing about the desired reaction. is passed through branch line Il to the dispersion The present invention is directed to amethod of chamber il. regenerating such powder to restore its activity The dispersion oi regenerating gas and powder for further use in the cracking operation.- In formed in the dispersion chamber Il must .be n order 'to restore the activityof the catalyst, it is under at least a 'pressure suilicient to overcome a practice to subject the catalyst to an oxidizing the pressure drop through the regenerating cirgas to burn` the' carbonaceous deposits from the 20 cuitor at least through certain stagesof the recatalyst. This regeneration can be accomplished, generating circuit. It is therefore necessary to for example, by suspending the catalyst containimpose the desired pressure on the powdered maing the combustible deposits in a streamvofoxiterialbeing introduced into the dispersion zone. dizing or vregenerating gas and passing the re- This can be accomplished, for eicarnple,` by consulting stream through a regenerating zone folstructing the `conduit; i3 in the form of a vertical lowed by separation of the regenerated catalyst standpipe in which the spent catalytic material from the regenerating gas. During the course is maintained in a freely iiowing state.` In such of such regeneration, however, it is necessary to case a pressure is developed at the bottom of the regulate .carefully the temperature thereof toY -standpipe vand the height of the tower can be maintain the same below a maximum beyond regulated so as to provide suiiicient pressureat which the activity of the catalyst. would be rethe bottom thereof to feed the powdered material duced. into the dispersion chamber Il. ln order to One of the principal objectsof the present inmaintain the spent catalyst in `a freely flowing vention is to provide an improved method of restate in the vertical standpipe I3, a iuidizing gas generation of catalyst of this character in which may be introduced into the column at one or theregeneration can be carried out more rapmorevertical points as shown. Thisfiiuidizing I idly and eiciently with minimum of operating gas may be an inert gas such as steam, nitrogen, equipment. A carbon dioxide, or the like. or it may be a gas `Other objects and advantages of the invention capable of having a modifying eilect on the catawill be apparent from the more detailed descrip- 4o lyst. l Y n v tion hereinafter, in which reference will be made In addition to, or in lieu of the fresh regenerto the accompanying drawing which is a diaating air added to the dispersion chamber il grammatic illustration of an apparatus suitable through line I6, compressor il and line i8, a for carrying the invention into effect. r portion of the gas employed in the final stages of Referring to the drawing, the reference charregeneration may be introduced into the disperacter IIJ designates a storage hopper in which sion chamber I4 through line "merging with the spent catalyst to be regenerated is collected. line i5 as later described in more detail.v Such catalyst may, for example, .be segregated The suspension of regenerating gas and powirom cracked products ,whichI have previously dered catalyst to be regenerated passes from the undergone a cracking operation. For example, dispersion chamber I4 through line 2l into a the cracked products containing the catalyst in first-stage regenerator22 in which the mixture is n suspension therein may be introduced into a suitmaintained for a period insufficient to regenerate able separator such as a cyclone separator locatcompletely the powdered material. `ecl in the top of the hopper il through line Il. The velocity oi' the regenerating gas carrying the powder therein passing through the iirstthe tower.

passes romthe conduit 26 into a second disper- 1 sion chamber-29.111 which it is mixed with addistage regenerator l! may be sufllcientl! high so that the residence time of the powder in the regenerating sone is not appreciably longer than the length of time of the' regenerating gas therein. Itis preferred, however. to pass the regen.

erating ses at relatively low velocity such as below 10 feet per second so that the time', of residence 4 iilis'hed. This regenerating chamber maybeof thesemeconstructionasthatintheiirststagoof regeneration and the velocity of the regeneratof the catalyst'within the regenerator 22 is mavterially longer than the time required for the passage of regenerating gas therethrough. In other words, the concentrationof the powder in the regenerating gas undergoing regeneration within the regenerator is materially higher' than the concentration' in the stream ofregenerating v,

gas and powder passing thereto. For example. the density of the material within the regenerator should be at least twice the ldensity of the nia-.- terial passingltheretoland preferably materially when l In any zone 22 pass. through' line 2 4 to a cyclone separator 24 or other' suitable separator' for the event the regenerating -gaa and powder g afterpassing through the first-stage regenerating segregation. of the regeneration gas from the'- powder.l The regenerating gas segregated from:

the powder in the cyclone 24 is removed therefrom throughline 25 and may be rejected. from the system or .may be passed through'further purification equipment for the final-separation of powdered material from the gas. Such'further purificationV equipment. for example. may v comprise 'additional cyclone separators, 4Cottrell precipitators, lter bags. or the like.'

During the course o! passage of through the regenerating none22, thetemperature is `increased to a material extent. For example, the temperature of the suspension passing into the regenerator may 1be of the order of from 'l00 to 850 F. and the temperature of the products leaving the `iiist-stage regenerator may beof theorder 'of 1000 to 1200 I'.

In view of this, it is desirable in moet cases to subject the partially regenerated catalyst segreing gas passing therethrough may be controlled in the same manner. The suspension of regenerating gas and powder after passing through the second-stage regenerator 34 passes through line il to afurther separator It in which the powder l is separated from the regenerating gas. The regenerating gas employed-in the second stage of regeneration 'is removedfrom the separator Il l through line 31. vThis product may be rejected from the system through line Il. This regenerat ing gasA in many cases. however, may have excess of oxygen which may be employedto advantage .in carrying out thein'itial stages of regenerationv and since it maybe at a higher pressure than the pressure of the rst stage of regeneration. it may be passed through line 4| and line Il to the dispersion chamberI I4 and there lntermixed with fresh regenerating gas and *spent-catalyst passing to the drst regenerating sone.

Powder separated in the second cyclone 30 be passed through a conduit 42 to a .further dispersion chamber 43 and there intermixed with additional regenerating 'gas introduced through line 44. If desired, the product passing through a ingto reduce the ,temperature thereof before f gated in the first cyclone 24 to a cooling treatment prior to passing the isame to the next stage of regeneration To accomplish this the catalyst separated in the cyclone 24 vmay discharge into a vertical column! 2t. which is surrounded by a cooling jacket 2 8 into which a cooling agent of any suitable character maybe-introduced and-removed. Ihe conduit-2i .may take the form ofa vertical standpipe '#lmilding up additional pressure'on the powdergpnior to passing the same to further regeneration. 'In such case, it may be-de'sirable to add sa .fuidizlng gas at one or more `spaced points alongfthe column 26 to maintain the powder in freely flowing condition to develop thus the desired pressure at the bottom of The' partially regenerated catalyst tional regenerating gas introduced through line 3 I. This regenerating gas`stream may, for example, consist of fresh air introduced through lineand compressor- I1 and branch line 3|, or it may' consist cfg-a stream of gas which hasl already been employed for carrying out the final stages of regeneration as described in more detail hereinafter. This recycle gas may, for example, be introduced into the dispersion chamber 29 through line 32. In any event, the dispersion of partiallyregenerated powder and regenerating gas formed in the dispersion chamberl 29 passes through line 33 to a second-stageregenerating -in the separator 40 fis withdrawn therefrom the vertical' conduit-42 may be subjected to coolpassing to the final stage of regeneration. `To

level before passing. to the dispersion chamber 43. v A l The regenerating gas admixed with the powder in the dispersionchamber," is preferably un- 40 diluted air and may evenbe enriched with oxygen or other oxidizing gasbefore being admixed with the powder. The dispersion of powder and regenerating gas formed in the dispersion chamber 4I passes through'line 4lzto a final-stage regenerating chamber v4-'l -`inwhich .the regeneration is completed. AHere, too.V the velocity of the regenerating gas may bev controlled asdescribed in connection with the first regenerating none to maintain the powder within the regenerating f zone forany desired period `to complete the regeneration. s' The 'suspension of regenerated catalyst and gas removed from the iinalregenerating chamber 41 passes through line 4ly to a suitable separator such as a cyclone separator 4l in which' the regenerated catalyst is segregated from the regenerating lges. The -regenerated catalyst separated through line il and may be passed in a continuous mannerto a suitable catalytic cracking unit (not shown). 'The regeneratinggas separated from the regenerated catalyst in the cyclone separator 49 is withdrawn therefrom through line 52 and may be'v rejected from the system through line. 53. However, this gas normally contains a substantial excess of oxygen which may be used 4to advantage in carrying out either the first or second stages of regeneration. To this end the regenerating gas or a portion thereof from the separator may be passed through lines l2, I4 and l2 to the inlet of the dispersion chamber 29 and there intermixed with powdered catalyst which has undergone the initial stages of regeneration. --As a furtheralternative, the regenerating gases recovered fromthe nal stages of rezone34 in which furtherregeneration is accom- 475 generation or a portion thereof may be passed through lines sz, s4, is, 4| yam is to the dispersion chamber ,I4 in which it is mixed with spent catalyst with or without fresh air introduced through line I8 prior to passing the same to the rst regenerating zone 22.

One of the important features of the present i pressure built up on the powder between the inf dividual stages of regeneration can be developed by the use of suitable vertical towers as illustrated, or other equivalent devices for imposing pressure on powder may .be employed in -lieu thereof, such as compression screws, pressure hoppers, and the like. f

It has previously been known that the time required for removing a given amount of combustible deposits from the catalyst mass is a function of the amount of such combustible deposits thereon. From this it follows that as the regeneration proceeds the rate of reaction tends to diminish unless further compensating action is taken. In accordance with the present invention, the regenerative reaction is accelerated in the final stages of regeneration by increasing the oxygen concentration of the regenerating gas and by increasing the total pressure on the ret generating gas stream which in turn increases` oxygen in the regenthe partial pressure of the erating gas.

Having described the preferred embodiment of the invention it will be understood that it embraces such other variations and modifications as come within the spirit and scope thereof.

This application is a continuation-in-part of copending application Serial No. 378,584, filed separating the partially regenerated contact mazone, controlling the conditions within said regenerating zone to partially regenerate said material during passage therethrough, thereafter terial from said regenerating gas, introducing said partially regenerated contact material into a second stream of regenerating gas containing free oxygen, passing the resulting mixture through a second Vregenerating zone separate and independ 'ent from said first-named regenerating zone while simultaneously introducing a fresh suspension of iinely-divided contact material containing combustible contaminants into said first regenerating zone, regulating the conditions in said second# f' named zone While maintaining a higher inlet oxygen concentration -than in Vsaid first-named regenerating zone to further regenerate said contact material and thereafter separating said contact material from said second stream of regenerating gas, the regenerating operations with relatively low and high inlet oxygen concentration in said first and second regeneration zones respec tively taking place simultaneously.

2. Method according to claim 1 in which the suspension of contact material and regenerating gas is passed upwardly through each regenerat-l v ing zone while .controlling the. velocity of the regenerating gas so that the time of passage of the contact material through the regenerating zone is materially14V greater than the time of the passage of the regenerating gas.

3. Method according to claim 1 in which the regenerating gas separated from the contact material removed from the second regenerating zone. is passed to the first regenerating zone.

WILLIAM I. THOMPSON. CHARLES .W. TYSON.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name i Date 1,577,534 Miller Mar. 23, 1926 2,199,838 Tyson May 7, 1940 2,273,076 Voorhees Feb. 17, 1942 2,311,564 Munday Feb. 16, 1943 2,320,273 Gohr et al. May 25, 1943 2,327,489 Becker Aug. 24, 1943 2,434,602 Thompson Jan. 13, 1948 

